Help with trailer wiring: It works when first wired-up, then stops working

[T.C.]

I'm having trouble wiring up the lights on a trailer. I have a 4-way connector, and I believe I've wired it up correctly:

- White to the trailer frame
- Brown to the tail lights
- Yellow to the left turn signal
- Green to the right turn signal

I verified this wiring against the instructions at http://www.therangerstation.com/tech...erLights.shtml. Unfortunately, it doesn't work. The tail lights, left turn signal, and right turn signal work when I first wire them up, but not afterward.

To elaborate: If I turn on the left turn signal on the car, then connect the yellow wire, the left turn signal on the trailer works fine, but only until I turn off the turn signal at the car. After that, the left turn signal on the trailer is unresponsive when I turn the turn signal back on. The same is true of the right turn signal and the tail lights -- they work as expected when I first wire them up, but stop working as soon as I turn off the turn signal or lights.

In all cases, I can disconnect the wires and reconnect them exactly as before, and the lamp in question will work properly again... until I turn it off and try to turn it back on. This tells me I haven't burned out a bulb or a fuse. At all times, the car's tail lights and turn signals work exactly as they are supposed to.

I am baffled by this. Does anyone have an explanation for why my trailer lights might work when first wired-up, but then stop working?

Some details: The car is a 1996 Nissan Pathfinder. The wiring harness on the car is an aftermarket T connector which I installed myself (see https://www.carid.com/curt/3-wire-t-...mpn-55361.html).

-TC

[aleekat]

I would check the continuity of the ground on the vehicle that you used.

[brcidd]

"Ditto" Bad ground is most common trailer lighting issues.

[T.C.]

Thank you for the suggestions. However, it looks like I have good continuity to the ground. I used an ohmmeter to measure the resistance between the ground of the flat connector and one of the bolts underneath the plastic threshold for the rear hatch (the only place I could find exposed metal). The meter read 0.9Ω. My meter has a continuity test feature which sounds a tone when there is low resistance. Using that feature, there was a strong, continuous tone. If I should be testing the ground wiring some other way, please let me know.

Is it possible that my T-connector is defective? (https://www.carid.com/curt/3-wire-t-...mpn-55361.html) The T-connector includes a literal black box that was described as 'a circuit-protected converter'. Might that be 'protecting' the circuit by shutting it down, perhaps in the way a ground fault interrupt does?

[aleekat]

Website says it has a one year warranty. I would contact the manufacturer. They may have seen this before.